Modeling and Checking Corner Braces#

A corner block (boxcorner) connects the adjoining trusses, but does not automatically provide sufficient spatial bracing. Under wind load, the frame can move laterally or the corner block can be subjected to high bending loads.

A corner brace, meaning a diagonal brace at the corner, forms a triangle with the adjoining components. This directs part of the lateral action through the diagonal as axial force and relieves the corner block.

Inserting a Corner Brace as a Pipe#

A pipe is suitable when the real assembly uses a tube or corresponding rigid brace capable of carrying both compression and tension.

1. Open the New Object tool in the Toolbar.
2. Select Connection > Pipe.
3. Click the first and second connection points of the diagonal.
4. Repeat the process for additional diagonals if the real assembly has a cross or bracing for several directions.
5. Select the inserted pipe and assign the cross section actually used under Override Cross Section.
6. Run the structural calculation again.

The pipe endpoints must be connected to the intended structural nodes. A diagonal that merely appears to touch a truss does not transfer force in the calculation.

If the new pipe remains gray in the Renderer, it often lacks a valid cross section. Check the Object Properties and the displayed structural errors. Use the cross section of the corner brace installed in reality rather than blindly copying one from an example.

Modeling a Corner Brace as a Rope#

A diagonal rope can also brace the frame effectively when it runs from the corner area to a suitable lower attachment or ballast point. The resulting triangle converts the lateral movement into axial force in the rope.

Keep the following in mind:

• A rope can transfer tensile forces only.
• With the opposite wind direction, the rope may unload and become slack.
• Opposing ropes or additional bracing may therefore be required for multiple wind directions.
• Both endpoints and the lower attachment point must match the real assembly in the model.

A single rope diagonal may only be considered sufficient if it is effective for the investigated load case and all other governing load cases are also covered by suitable components.

Base Plate and Ballast as an Additional Measure#

A larger base plate and additional ballast can improve the support condition at the floor. This can reduce the bending moment at the upper corner block because a larger share of the action is already resisted at the base.

However, this measure has a different structural effect from a corner brace:

Measure	Effect in the model	Important prerequisite
Rigid corner brace	Transfers tension and, where applicable, compression through a diagonal	The real component and its connections must be capable of carrying these forces.
Rope diagonal	Transfers tensile force and forms a triangle for one load direction	The rope must be tensioned and attached at the actual connection point.
Larger base plate or ballast	Changes support conditions, uplift resistance, and overturning behavior at the base	Weight, dimensions, friction, and anchoring must be applied correctly.

Ballast does not automatically replace missing diagonal bracing. Likewise, a support in the model must not resist tension if it is not anchored in the real assembly.

Checking the Effect of the Bracing#

Check the entire structural system after every change:

1. Enable the 3D result display.
2. Check whether the diagonal is part of the connected system.
3. Compare deformation and utilization before and after inserting the corner brace.
4. Check the axial force in the diagonal and the load on the corner block.
5. Check the support reactions for negative values and thus possible uplift.
6. Repeat the check for all governing wind directions.

The result is plausible if the diagonal actually carries force, the lateral deformation decreases, and no new impermissible loading occurs at another component or support.

Note: Model checking does not replace a structural verification or qualified assessment of the real connections. In particular, compression braces, ropes, ballast, and anchors may only be applied using their verified actual properties.

Further Information#

• Understanding and Checking Wind Loads explains how wind forces are created and distributed.
• The calculation and its result displays are described under Structural Calculations.
• For the fundamentals of internal forces and deformation, see Forces, Moments, and Deformation.